Abstract: A thermo- and photo stable composition comprising a chitosan/xanthan hydrogel including at least one thermo- or photo-sensitive substance chosen among the following: vitamins, amino-acids, nucleic acids, and polypeptides. The hydrogel can be adapted to release the thermo- or photo-sensible substances in either a human or an animal. The present invention also discloses a method of making these hydrogel composition. Additionally, the present invention presents a method of using these hydrogel composition in dermatology or as a food supplement.

Abstract: The present invention relates to a method for modifying the solubilization rates of poorly water soluble drugs, using a chitosan-xanthan hydrogel. In addition, the present invention relates to a process for the preparation of chitosan-xanthane hydrogels as well as for the preparation of hydrogels comprising a poorly water soluble drug.

Abstract: A supported polyionic hydrogel is prepared by impregnating a support matel with a solution of anionic polysaccharide and a solution of cationic polysaccharide where the anionic polysaccharide and cationic polysaccharide react with each other to form a polyionic hydrogel impregnated in the support material. The hydrogel may be dried such as by lyophilization. Preferably, the anionic polysaccharide is xanthan, dicarboxystarch or dicarboxycellulose and the cationic polysaccharide is chitosan. Especially preferred is a polyionic hydrogel formed from xanthan and chitosan. A paper material or a textile material can be used as the support material. A dry supported polyionic hydrogel can be formed as a bandage without active material incorporated therein. The supported polyionic hydrogel may be formed containing a biologically active material by having the active material in either polysaccharide solution or in another solution impregnated into the support material.

Abstract: A supported polyionic hydrogel containing biologically active material is epared by impregnating into a porous support material a solution of anionic polysaccharide, a solution of cationic polysaccharide and a biologically active material. The anionic polysaccharide and the cationic polysaccharide react with each other to form a hydrogel containing the biologically active material. The hydrogel may be dried such as by lyophilization. The biologically active material can be in either polysaccharide solution or in another solution impregnated into the porous support material. A paper material or a textile material may be used as the porous support material. Preferably, the anionic polysaccharide is xanthan, dicarboxystarch or dicarboxycellulose and the cationic polysaccharide is chitosan. Especially preferred is a hydrogel formed from xanthan and chitosan.

Abstract: A method for the preparation of insoluble hydrogels from the complexation of polycations and xanthan is reported. Stable hydrogels capable of retaining between 65 and 95 % weight water were prepared particularly with chitosan and xanthan. The water retention and properties of the hydrogels were studied as a function of the degree of acetylation of chitosan and the ratio chitosan/xanthan used in the preparation of the gel. The chitosan-xanthan complex was used to immobilize biological material. Hydrogels containing enzymes (for example endo-1,4-.beta.-xylanase and protease) either as single enzymes or as a binary system have been prepared. Immobilization varied between 85 and 98 % . The immobilized xylanase activity was significantly greater with respect to the free enzyme while the binary enzyme system promoted protease activity. Other hydrogels prepared with polybasic drugs complexed to xanthan with or without chitosan have been prepared.